1. Field of the Invention
This invention relates to a method for the preparation of .alpha.-hydroxymethylene nitriles and .alpha.-formyl nitriles or their tautomers of the formulae ##STR4## as well as their corresponding alkali and alkaline earth metal salts especially salts of the formula Ia by reaction of the corresponding nitriles with carbon monoxide in the presence of an alcoholate. This invention is further directed to certain new and useful .alpha.-hydroxymethylene nitriles or .alpha.-formyl nitriles or their tautomeric mixtures or their salts or mixtures of their salts. This invention is particularly directed to a method for preparing such nitriles in an economically feasible manner whereby the nitriles are obtained in a relatively high yield.
2. Discussion of the Prior Art
The preparation of .alpha.-hydroxymethylene nitriles is difficult in the present state of the art.
A number of compounds of General Formulas Ia and Ib are formed, according to Ann. 512, 97-111 (1934) by the reaction of aliphatic nitriles with formic acid esters in the presence of alkali metals and alkali alcoholates, respectively. The yields, however, are low.
According to Bull. Soc. Chim. France, 1961, 1144-7, .alpha.-formyl-.alpha.-phenylacetonitrile can be isolated by the reaction of benzyl cyanide with formic acid ester in the presence of sodium alcoholate.
Unsatisfactory in these methods of preparation are the poor yields and the handling of formic acid esters, which are highly volatile and very toxic.
Other methods, such as the reaction of isoxazoles ##STR5## wherein R.sup.2 represents CH.sub.3 and phenyl, with alkali alcoholates (C.A. Vol. 50, 6432 (1956) and the preparation of cyanacetaldehyde from malonic aldehyde dioxim (German Ofenlegungsschrift No. 1,920,346) in several steps, are difficult and uneconomical.
By the hydroformylation of acrylonitrile with hydrogen and carbon monoxide (J. Chem. Soc. D, 1970, 1255) in the presence of Co.sub.2 (CO).sub.8, .alpha.-formylpropionitrile is obtained in a 7.8% yield. Aside from the pressures required in hydroformylations, .beta.-isomers are formed preferentially. This method can be applied to only a very few compounds.
It is an object of the present invention to prepare .alpha.-hydroxymethylene nitriles and .alpha.-formyl nitriles in high yields and in an economical manner by a process that can be performed economically and commercially.